In general, a shelf for a showcase, which is placed in convenience stores and the like, is to display goods at a front end thereof for a purchaser to distinguish and select the goods conveniently. As the purchaser takes one of the goods from the front end of the shelf, a next one positioned behind the taken one becomes moved to the front end by sliding due to a down-slope from a rear end toward the front end of the shelf which is slant by an inclination angle. The shelf is mounted with a plurality of rollers on a bottom surface contacting the goods for the movement of the next good toward an empty space previously occupied by the first good which is taken by the purchaser, and guide elements for defining spaces for displaying the goods as being aligned in lines.
Korean Utility Model Reg. Pub. No. 20-0327237 of the present inventor discloses a shelf for a showcase including a plurality of rollers for first-in and first-out of displayed goods, as shown in FIG. 11 to FIG. 15.
Referring to FIG. 11 and FIG. 13 respectively showing an exploded perspective view and a cross-sectional view of an improved shelf 1 for a showcase having in a plurality of rollers 3 coupled for sliding movement of goods secured on the shelf, includes a roller unit 2 formed of a U-shaped roller plate 23 having a plurality of fitting grooves 22 at both side walls 21 to rotatably insert mounting shafts 31 protruded at both side ends of rollers 3, a casing 4 having both side walls 41 respectively formed with a rib 42 for closing opening parts of the fitting grooves 22 of the roller plate 23 to prevent deviation of the rollers 3 after the rollers 3 are fitted into the roller unit 2, and a bottom surface 43 connecting the side walls to each other and formed with chilled air ventilation holes 44, end caps 5 coupled with front and rear ends of the casing 4, and guide elements 9 formed with metal or synthetic resin materials and fitted into insertion grooves 51 of the end caps 5 at both ends to serve as barriers.
The prior art shelf for a showcase has, however, problems not only in machining, assembling and continuous connection of such roller units but also in the structure causing high expenses relating to raw materials and machining. In the shelf 1, each of the component parts is formed with aluminum metal or synthetic resin materials by injection molding, extrusion, die-casting, pressing and the like. The roller unit 2 includes the roller plate 23, which is injection-molded to have the fitting grooves 22 at the side walls for mounting the mounting shafts 31 of the plurality of rollers 3 and the plurality of chilled air ventilation holes 24 in the horizontal bottom surface by a uniform interval. This roller unit 2 is publicly-known in the art and widely used due to the convenience in the mounting of the plurality of rollers 3. The casing 4, which prevents deviation of the rollers 3 and promotes smooth sliding of goods by fitting the rollers in the roller unit 2, is formed with aluminum materials having high durability by extrusion to bear loads of the roller unit 2 and displayed goods. The end caps 5 screw-coupled with the front and rear ends of the casing 4 are injection molded. The guide elements 9 are formed with synthetic resin materials by injection molding or a metal plate by pressing.
The casing 4, one of the component parts of the prior art shelf 1 for a showcase, is formed by continuous extrusion in the lengthwise direction and cut by a predetermined length. The casing 4 is formed with chilled air ventilation holes 44 in a bottom surface 43 correspondingly to the chilled air ventilation holes 24 of the roller plate 23 of the roller unit 2 by pressing so as to promote smooth circulation of chilled air. The casing 4 is formed with holes 45 at the front and rear ends by punching to insert coupling screws 8 for fixing the end caps.
The prior art shelf 1 for a showcase has a disadvantage in the expense since the casing 4 is extruded as a single element incurring high raw material expense and pressed to form the chilled air ventilation holes 44 incurring additional expenses for machining and finishing of the chilled air ventilation holes 44.
Further, if the casing 4 has a central wall 46 formed with a rib 47 at an upper end thereof to align the roller units 2 in two lines in the casing 4 for the smooth sliding of relatively large-volumed goods on the roller units 2, as shown in the cross-sectional view of FIG. 14, the above expenses for the raw materials and the pressing and finishing of the chilled air ventilation holes 44 may be increased by double or more. Furthermore, in order to increase the alignment lines of the roller units 2 to 3 to 6 lines to provide a wide sliding area for frequent adjusting of display intervals of goods or for the display of the large-volumed goods, as shown in FIG. 15, the size of the casing 4 mounted with the central walls 46 and the ribs 47 by a uniform interval has to be increased according to the quantity of the roller units 2. In addition, it is difficult to keep smoothness during the extrusion of the casing 4 in the increased size, so that the casing 4 is apt to be distorted. It is impossible to assemble such the defect casing 4 due to the defect in the extrusion. Therefore, the casing 4 is disadvantageously limited in the small size to align the roller units 2 only in a single line or two lines.